This disclosure pertains to detecting mass, i.e. weighing, a discrete physical item while it is moving. In particular, improvements are disclosed for automated, high-speed, precise weighing of moving objects. The improvements may be implemented in robotic systems and other applications. In our previous work, beginning with U.S. Pat. No. 7,687,727, the primary indicator of mass magnitude is the amplitude of the torque response from the servo system when instructed by a control system to change the speed of a moving item with some unknown mass. The torque signal can be an impulse or a composite of harmonically related sinusoids or other time varying signal. The torque amplitude is tightly correlated with the mass of the moving item and is used to produce a useful measurement of its mass. This is a type of amplitude modulation or AM approach. As with other technologies that rely on amplitude modulation schemes, these torque signals are subject to distortion and noise from a number of sources. In addition, the cited patent applies only to individual discrete items; they must be weighed one at a time. The disclosure that follows solves this and other problems and limitations.